Known prior art self righting drinking cups are disclosed by U.S. Pat. Nos. 2,601,767, 4,303,170, 4,388,996 and U.S. Pat. No. 216,730. These prior art devices disclose a single piece cup having an integral weighted convex base member for righting the cup. The weighted base on these prior art devices is not removable.
U.S. Pat. No., 4,096,966 teaches a self righting drinking cup having a separate removable convex weighted base so that the cup may be used as a conventional cup. However, the base member is adapted to engage the cup to form a push or screw fit. The objective of the instant invention is to provide positive engagement between the base member and the cup providing a more secure attachment of the base to the cup than a push fit, and to provide a quicker and easier release and attachment than a screw fit.